Chemical Pressure-Driven Band Convergence and Discordant Atoms Intensify Phonon Scattering Leading to High Thermoelectric Performance in SnTe

Hongwei Ming; Zhong-Zhen Luo; Zixuan Chen; Hong-Hua Cui; Wenwen Zheng; Zhigang Zou; Mercouri G Kanatzidis

doi:10.1021/jacs.4c10286

Chemical Pressure-Driven Band Convergence and Discordant Atoms Intensify Phonon Scattering Leading to High Thermoelectric Performance in SnTe

J Am Chem Soc. 2024 Oct 3. doi: 10.1021/jacs.4c10286. Online ahead of print.

Authors

Hongwei Ming¹, Zhong-Zhen Luo^{1

2

3}, Zixuan Chen², Hong-Hua Cui⁴, Wenwen Zheng^{3

5}, Zhigang Zou^{1

2

6

7}, Mercouri G Kanatzidis³

Affiliations

¹ Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108, China.
² Key Laboratory of Advanced Materials Technologies, International (HongKong Macao and Taiwan) Joint Laboratory on Advanced Materials Technologies, College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, P. R. China.
³ Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
⁴ Mechanical and Electrical Engineering Practice Center, Fuzhou University, Fuzhou 350108, China.
⁵ Hubei Key Laboratory of Optical Information and Pattern Recognition, School of Optical Information and Energy Engineering, Wuhan Institute of Technology, Wuhan 430205, P. R. China.
⁶ Eco-materials and Renewable Energy Research Center, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China.
⁷ National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.

PMID: 39360889
DOI: 10.1021/jacs.4c10286

Abstract

SnTe is an intriguing alternative to PbTe for midtemperature thermoelectric applications. Despite steady progress, its performance is lagging, in part because of the large energy difference(ΔE_L-Σ) between the light (L-band) and heavy (Σ-band) valence bands and higher lattice thermal conductivity (κ_L). Previous studies have shown that applying pressure can enhance the Seebeck coefficient (S) and power factor (PF) of SnTe. Inspired by this study, we showcase how the high-pressure effect can be emulated under ambient pressure by substituting Sn with atoms possessing smaller atomic radii. Specifically, Sb- and Ge-doping combined with CdTe- or CdS-alloying induce lattice shrinkage, also referred to as "chemical pressure", raising the energy of the Σ-band. Additionally, these substituted atoms lower the contribution of Sn 5s-Te 5p antibonding states to the L-band, thereby reducing its energy and dispersion. These combined effects decrease ΔE_L-Σ from 0.36 to 0.09 eV, leading to the enhanced S and average PF_avg. Notably, the PF_avg, ranging from 323 to 873 K, increases from 8.1 μW cm^-1 K^-2 for pristine SnTe to 21.6 μW cm^-1 K^-2 for Sn_0.79Ge_0.15Sb_0.06Te-5% CdTe. Furthermore, the intensified phonon scattering resulting from discordant nature of Ge and Cd atoms, creating point defects soften phonon modes, and the presence of Ge-rich nanoprecipitates lead to a substantial 62% reduction in κ_L at 873 K. This strong valence band convergence and enhanced phonon scattering collectively contribute to a high peak ZT of 1.5 (873 K) and high average ZT_avg = 0.81 over the temperature range of 323-873 K.